Non-invasive imaging of neuroanatomical structures and neural activation with high-resolution MRI.

Non-invasive imaging of neuroanatomical structures and neural activation with high-resolution MRI.

Herberholz J, Mishra SH, Uma D, Germann MW, Edwards DH, Potter K.

Front Behav Neurosci. 2011 Mar 31;5:16.  PMID: 21503138

In their previous work, the authors of this paper had shown that traditional MRI was not powerful enough to resolve structures in crayfish brain.  In this paper, the authors showed that manganese-enhanced MRI (MEMRI) offers the ability to resolve the structures that could not be visualized by traditional MRI.  They also compared the results of two different imaging systems (14.1T and 9.4T) and found both to have sufficient power to yield reliable results.

The authors of this paper gave juvenile crayfish, which lack blood barriers, injections of manganese (various concentrations) directly in to the hemolymph over 2-3 minutes. Imaging was performed after varying times (15-30mins) in order to allow neuronal uptake of manganese. Some crayfish had one antenna nerve stimulated throughout the injection and during the “waiting period” to examine activity-dependent manganese uptake.  To prevent motion artifacts, some crayfish had their cephalothoraces embedded in agarose during imaging, which was removed before return to their home tanks.

Some of their more interesting results were that while T1-weighted images could show differences in activity-dependent uptake, T2-weighted images were unable to show those differences, but still allowed them to visualize structure better than traditional MRI.  They also found a range of uptakes, ipsi/contralateral stimulation-induced differences, and signal-to-noise-ratios between individual crayfish, seemingly to be due to differences in basal activity and response to assorted stimuli.  This is a point to consider and something that I imagine we will encounter in our own MEMRI studies.

-DH